Objective The coaggregation abilities of 4 strains of periodontal pathogens Fusobacterium nucleatum（ F.nucleatum）, Porphytomonas gingivalis（P.gingivalis）, Prevotella intermedia（P.intermedia） and Haemophilus actinomycetemcomitans（H.actinomycetemcomitans） were compared. The changes of the ability of periodontal pathogens attaching to artificial root surface mediated by F.nucleatum were observed in order to investigate the possible interaction of the bacteria in periodontal biofilm. Methods The coaggregation degree among 4 strains of periodontal pathogens was investigated by a visual assay. Differences of the adherent percent of periodontal pathogens to collagen- coated hydroxyapatite（c-HA） under two conditions when F.nucleatum had already bond to c-HA and when F.nucleatum had not, were detected by radioisotope scintillation counter. Results The coaggregation among 4 studied strains was observed. The coaggregation degrees between F.nucleatum and P.gingivalis, as well as between P.gingivalis and P.intermedia reached 4. The coaggregation degrees of F.nucleatum with the other three bacteria were higher than 3. The adherent percent of P.gingivalis, P.intermedia and H.actinomycetemcomitans to c-HA when F.nucleatum had already bond to c-HA were higher than that when F.nucleatum had not. The adherent percent of F.nucleatum to c-HA when F.nucleatum had already bond to c-HA were lower than that when F.nucleatum had not. Conclusion The periodontal pathogens coaggregate. F.nucleatum may play a role as a bridge in the colonization of the other periodontal pathogens in the periodontal biofilm.
